时间：2019-05-10标签：asp.netSystem.Net.Mail.SmtpFailedRecipientException

Question

I've a problem. I was sending newsletters to my users, I've more of 10000 email addresses. When i tried to send it with only 6/7 email it worked, now it doesn't work anymore. Why? I receive this error:

Exception Details: System.Net.Mail.SmtpFailedRecipientException: Mailbox unavailable. The server response was: 5.1.1 Too many bad domains

[SmtpFailedRecipientException: Mailbox unavailable. The server response was: 5.1.1 <rsv1979@yahoo.com> Too many bad domains]

[SmtpFailedRecipientsException: Unable to send to a recipient.]
   System.Net.Mail.SmtpClient.Send(MailMessage message) +1648
   Admin_InviaNewsLetter.SendEmailButton_Click(Object sender, EventArgs e) +3013
   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +118
   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +112
   System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5563

I can't understand why! If u need the code, here it is:

for (int i = 0; i < 501; i++)
    {
        destinatario = HttpUtility.HtmlDecode(Convert.ToString(Convert.ToString(dt.Rows[i][0])));
        msg.To.Add(destinatario);
    }
    string body = HttpUtility.HtmlDecode(BodyMessageTextBox.Text);
    msg.From = new MailAddress("email@address.it");
    msg.Subject = HttpUtility.HtmlDecode(ObjectTextBox.Text);
    msg.IsBodyHtml = true;
    msg.Body = pzzsopra + body + pzzsotto;
    SmtpClient sc = new SmtpClient("smtp.sitedomain.it");
    sc.Port = 25;
    sc.Credentials = new NetworkCredential("email@address.it", "");
    sc.EnableSsl = false;
    sc.Send(msg);

I hope to find the solution. Thank you before!

Answer 1

This could be a problem with that email address, in which case your loop logic needs to handle such errors, forget that one and proceed onwards. However it might be that your domain is blacklisted by the recipient mail server (or their infrastructure).

Try this for starters - http://www.aweber.com/blog/email-deliverability/whitelisting-feedback-loops.htm

In my experience, it's better to use a trusted 3rd party to send bulk emails. Try mailchimp or google for 'email campaign software' / 'email newsletter software' - there are lots of providers, most of which have API's your ASP.NET site can talk to.